1. Field of the Invention
The present invention relates to an antenna having a predetermined meandered slot on a ground plane of an RF module, and more particularly, to a meandered slit antenna that does not require an extra antenna attachment process when manufacturing a module such as an RF remote control.
2. Description of the Related Art
With the rapid development of the information communication technology, a wireless communication system has been changed from a system for just transmitting voice data into a system for transmitting various kinds of wideband data such as multimedia data. Furthermore, as the mobility of wireless communication is more emphasized, a wireless communication terminal used in the wireless communication system gradually is getting smaller and lighter.
Additionally, the attention for radio frequency identification (RFID) that plays an important role in ubiquitous technology has been increased. The RFID is a technology with a semiconductor microchip to process data and is a non-contact recognition system to wirelessly transmit and process information on objects and surroundings by attaching each microchip to various kinds of products. The RFID system that appeared at the 1980's is also known as dedicated short range communication (DSRC) or a radio frequency identification system. The RFID includes a scanner, a frequency, and a tag. The RFID system is characteristic of a wireless connection between the scanner and the tag. Also, the RFID can edit and add data to the tag, read a plurality of tags simultaneously, and have a high read rate under the poor condition such as coldness and warmth, humidity, dust, or heat.
Moreover, an antenna produces a radio signal when transmitting an electric signal generated in an electronic circuit into space, or converts a radio signal received from air into an electric signal at an electronic circuit. The former is called a sending antenna and the latter is called a receiving antenna. In a common communication system, the sending antenna plays the receiving antenna at the same time.
Additionally, when an antenna is used for transmission (radiation), various characteristics such as directionality and an operating frequency appear just like when used for reception. Therefore, the receiving antenna, assuming as a sending antenna for convenience of explanation, is used for explaining an operating principle of the antenna.
A dielectric substrate has a predetermined dielectric constant and thickness in a conventional slot antenna used in the RF remote control or the RFID tag. A slot is formed on one side of the dielectric substrate and has an half length of a center frequency wavelength λ for radiation of an electromagnetic field. A microstrip feed line is formed on other side of the dielectric substrate and supplies an electromagnetic energy to the slot.
On the other hand, a conductor line on a printed circuit board (PCB) is used as an antenna in a conventional antenna. However, a meandered antenna uses a conductor line on the PCB as an antenna when a frequency is relatively low. Consequently, it becomes very difficult to embody an antenna with an increase of a capacitive loading effect.
Also, when a conductor is disposed at an upper portion and/or a lower portion of a conventional antenna, there is a problem in that an amount of radiation of an electromagnetic wave decreases because a current canceling effect is influenced by an image current. Specifically, a current is cancelled out by an influence of an image current when the antenna is placed around a conductor such as a multi-layer substrate, a steel product, and a container. Additionally, the antenna uses an induced electric current on a conventional conductive surface, and the image current is caused by the conductive surface around an antenna or a ground plane. Consequently, there is a problem in that an amount of radiation or a frequency varies extremely.
Furthermore, a conventional antenna has a main lobe in a direction perpendicular to a ground plane of the antenna when a remote controller requires a large amount of radiation in a specific direction. Consequently, it is very difficult to radiate in a parallel direction as required.